The proposed project involves both psychophysical and computational investigations of human stereopsis and binocular vision. To date, most computional investigations have focused on solving the binocular matching problems while most of the psychophysics have focused on stereoscopic localization or stereoscopic form recognition. The broad goal of this project is to gain a greater understanding of the process of stereopsis by alleviating this imbalance. The specific aims of the proposed project are: 1) To investigate the psychophysical properties of the binocular matching process in human vision and to compare and contrast these properties with those of stereoscopic localization. 2) To explore the nature of disparity channeling in the human visual system. This includes: a) Developing computational models based on both the classical 3-channel theories of stereopsis and more recent theories based on larger number of channels. b)Testing both of the above types of models psychophysical using two types of tasks, those that involve binocular matching and those that involve binocular matching and those that involve stereoscopic localization. c) Reassessing the meaning of the clinical conditions of stereoblindness and stereoanomaly in light of the results of the above investigations. 3) To develop a computational model of stereopsis that incorporates a biologically plausible front end and that can make quantitative predictions about two types of psychophysical experiments, those involving binocular matching (e.g. correlation detection) and those involving stereoscopic localization (e.g. stereoacuity). The psychophysical experiments will involve one of two kinds of tasks. In the first type of task, observers will be required to make judgments concerning the interoccular correlation of dynamic random element stereograms, which will be generated and displayed on a microcomputer. No judgments concerning disparity or depth will be required. In the second type of task, observers will be required to make judgments involving stereoscopic localization under nearly identical stimulus conditions. The differential effects of various stimulus variables on these two types of judgments will be analyzed to distinguish the properties of stereopsis that are governed by the mechanisms of binocular matching from those that are governed by the mechanisms of stereoscopic localization.